Field of the Invention
The present invention relates to a method for producing brushes, in particular toothbrushes, in which a brush body is formed by injection molding in a mold cavity, bristle filaments are connected to the brush body for forming bristles, and at least one flexible cleaning element extending substantially in parallel with the bristle filaments is preferably formed by injection onto the brush body.
Such a generic method is e.g. known from U.S. Pat. No. 5,628,082. Apart from the conventional bristle filaments which, being normally combined into tufts of bristles, are held in the brush body, the brush additionally comprises cleaning elements, preferably made from a thermoplastic elastomer. The cleaning elements serve not only to clean the teeth and the neighboring gums, but also to massage the gums. Moreover, the cleaning elements improve the application of dentifrices. A brush which is produced according to the generic method and serves as a toothbrush is e.g. known from WO 96/15696. In this prior-art brush, defined areas are provided one after the other for flexible cleaning elements on the one hand and for tufts of bristles on the other hand in the longitudinal direction of the toothbrush. All of the useful ends of the tufts of bristles are located in the already known brush in one plane.
Up to today such a brush has not been accepted because it does not satisfy the actual demands. As a rule, the user expects bristles provided over the whole brush head. Moreover, not only the flexible cleaning elements should have a contour, i.e. an extension of the useful ends differing from the extension of the bristle surface of the brush, i.e. that surface of the brush body that is penetrated by the bristle filaments and/or the flexible cleaning elements.
Moreover, the prior-art method is relatively complicated. First of all, a brush body comprising recesses is produced by injection molding and, after the brush body has been removed, bristle filaments are connected thereto by clips introduced into the recesses. Following a possible finishing of the useful ends of the bristle filaments the brush body is again inserted into an injection molding tool and at least one flexible cleaning element is over-molded onto the brush body.
It is the object of the present invention to develop the method for producing brushes of the above-mentioned type such that brushes which comprise a combination of flexible cleaning elements and bristle filaments can be produced without restriction of the bristle field geometry and/or the contour of the bristles, and to provide an apparatus suited for performing the method.
To achieve the above object, the above-mentioned generic method is developed according to the invention such that the useful ends of the bristle filaments are finished, the flexible cleaning element being removed at least during the finishing process from the operative area of the finishing tool.
In the method according to the invention any desired bristle field can be formed on the brush, in particular the brush head of a tooth brush. Due to the finishing operation according to the invention a contour of the bristle field can be obtained by cutting. Moreover, the bristle filaments that are cut at a later time are rounded during the finishing operation. Bristle filaments already secured as contoured bristles by over-molding to the brush body can also be rounded within the scope of the finishing treatment. In the method according to the invention the flexible cleaning elements are removed from the operative area of a finishing tool, so that the bristles provided on the brush body can be adapted to the respective demands made on its use without the flexible cleaning elements impairing the finishing operation or making it impossible. Thus a brush that is provided with tufts of bristles and flexible cleaning elements and is substantially finished can be adapted to the respective demands made on its use without such an adaptation being impaired by the configuration of the flexible cleaning elements.
In comparison with the conventional method in which a bristle carrier is first produced in a first injecting molding step and is then provided with bristles after removal from the molding tool and in which the bristle filaments are then finished and the bristle carrier is then again inserted into an injection molding tool, the brush is first completed in the method according to the invention and the bristle filaments are then finished. The method according to the invention can thus be carried out very economically. It is here of no importance whether the bristle filaments are connected by over-molding or in a conventional way, i.e. via an anchor, to the brush carrier. The method can already be simplified considerably by the measure that the two injection molding steps, first the formation of the brush body and then over-molding of the flexible elements on the brush body, are carried out directly one after the other. It is only then that the brush is transferred from an injection molding area within the process line to further stations where the bristle filaments are possibly connected in a conventional way to the brush body and the ends of the bristle filaments at the fastening side are finally finished after previous removal of the flexible cleaning element(s) from the operative area of the finishing tool. In particular in the case of a strong entanglement between the bristles formed by the bristle filaments and the flexible cleaning element(s) provided on the brush body, it is however preferred that the bristle filaments are connected to the brush body during injection molding into the mold cavity by embedding their ends provided at the fastening side and projecting into the mold cavity. In the case of a dense arrangement of the bristle filaments and the flexible cleaning elements on the brush body, a later fastening of the bristle filaments past the flexible cleaning elements is at best possible under great efforts.
In particular when elongated cleaning elements are used, the flexible cleaning element should preferably be compressed in axial direction towards the brush body. While it is known in the prior art that individual tufts of bristles of a field of bristles are deflected laterally, the flexible element(s) are compressed in the axial direction of the bristle filaments towards the brush body in the preferred embodiment of the method according to the invention. While the lateral deflection of individual or several tufts of bristles as is known from the prior art for grinding and/or shortening other tufts of bristles leads to restrictions and not all of the desired tufts of bristles of the brush can be finished, all tufts of bristles of the field of bristles can be finished in the preferred method on the whole or also selectively. The flexible cleaning element is compressed in the axial direction of the filaments using the useful ends of the bristle filaments to be treated.
The displacement of individual bristle filaments as is known from the prior art is disadvantageous insofar as it cannot be ensured in a reliable manner that predetermined bristle filaments or groups of bristle filaments, i.e. tufts of bristles, are finished in a defined way while other bristle filaments are kept away from the treatment area of the finishing tool. This drawback is reliably avoided in a preferred embodiment of the method according to the invention in that the at least one flexible cleaning element is compressed by axially supplied wires and the useful ends of the bristle filaments are guided past the wires supplied. The wires impinging on the bristle filaments in linear fashion have an almost negligible width so that the bristle filaments are pushed past the wires, whereas the flexible cleaning element, in particular in the case of an elongated extension, is seized by the at least one wire and pressed onto the brush body.
The preferred embodiment of the method according to the invention, wherein at least one wire, preferably a plurality of wires, and particularly preferably a wire grating, is supplied in the axial direction of the brush filaments to the brush body and the flexible cleaning element(s) is/are compressed in the axial direction of the bristle filaments, is preferably developed such that the bristle filaments are supported on the wires during finishing. The wires arranged above the bristle surface reduce the free bending length of the bristle filaments to be treated, thus improving a finishing of their useful ends in a predetermined way. An uncontrolled bending of the bristle filaments is in particular prevented when a close-meshed wire grating is used.
Preferably, the method according to the invention is developed such that the flexible cleaning element is gripped around on its free end for removal from the operative area of the finishing device. The displacement of individual bristle filaments which is known from the prior art cannot be carried out with the necessary accuracy. Individual bristle filaments to be displaced remain in the field of bristles and are subjected to a finishing operation in an undesired way, whereas other bristle filaments to be treated are removed from the operative area of the finishing tool.
In the preferred development of the method according to the invention, the flexible cleaning element(s) is/are gripped around at least in part in a defined way. This means that the flexible cleaning element is enclosed circumferentially at least in part. To this end gripping elements can be used that have actuable gripping surfaces. The preferred process, however, can be realized constructionally in a particularly simple way when a means is supplied towards the brush body, the means comprising at least one grip opening gripping around the flexible cleaning element. The flexible element is entrapped in said grip opening and preferably deflected laterally by operating the means which can be supplied. This reliably prevents the bristle filaments to be finished from being removed by mistake from the operative area of the finishing tool.
The object further underlying the invention, i.e. to provide an apparatus for performing the finishing operation for a brush comprising bristle filaments and flexible cleaning elements, without any limitation by the flexible cleaning elements provided on the brush body, can be achieved according to the invention in that the apparatus comprises a clamping device for the brush body and a means which is assigned to the clamping device and acts on at least one flexible cleaning element, the means being movable relative to the clamping device.
The present invention suggests, for the first time, an apparatus for finishing flexible cleaning elements and brushes comprising bristle filaments. The apparatus according to the invention comprises a means with which the flexible cleaning element can be removed from the operative area of a finishing tool, so that the finishing operation can be carried out without limitation by the flexible cleaning elements provided on the brush.